mirror of https://git.tukaani.org/xz.git
f644473a21
It also works on E2K as it supports these intrinsics. On x86-64 runtime detection is used so the code keeps working on older processors too. A CLMUL-only build can be done by using -msse4.1 -mpclmul in CFLAGS and this will reduce the library size since the generic implementation and its 8 KiB lookup table will be omitted. On 32-bit x86 this isn't used by default for now because by default on 32-bit x86 the separate assembly file crc64_x86.S is used. If --disable-assembler is used then this new CLMUL code is used the same way as on 64-bit x86. However, a CLMUL-only build (-msse4.1 -mpclmul) won't omit the 8 KiB lookup table on 32-bit x86 due to a currently-missing check for disabled assembler usage. The configure.ac check should be such that the code won't be built if something in the toolchain doesn't support it but --disable-clmul-crc option can be used to unconditionally disable this feature. CLMUL speeds up decompression of files that have compressed very well (assuming CRC64 is used as a check type). It is know that the CLMUL code is significantly slower than the generic code for tiny inputs (especially 1-8 bytes but up to 16 bytes). If that is a real-world problem then there is already a commented-out variant that uses the generic version for small inputs. Thanks to Ilya Kurdyukov for the original patch which was derived from a white paper from Intel [1] (published in 2009) and public domain code from [2] (released in 2016). [1] https://www.intel.com/content/dam/www/public/us/en/documents/white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf [2] https://github.com/rawrunprotected/crc |
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| .. | ||
| Makefile.inc | ||
| check.c | ||
| check.h | ||
| crc32_fast.c | ||
| crc32_small.c | ||
| crc32_table.c | ||
| crc32_table_be.h | ||
| crc32_table_le.h | ||
| crc32_tablegen.c | ||
| crc32_x86.S | ||
| crc64_fast.c | ||
| crc64_small.c | ||
| crc64_table.c | ||
| crc64_table_be.h | ||
| crc64_table_le.h | ||
| crc64_tablegen.c | ||
| crc64_x86.S | ||
| crc_macros.h | ||
| sha256.c | ||